HDDS-16472. [STS] Tighten session policy validation

[fmorg-git]

Please describe your PR in detail:

• There are edge cases in the IAM session policy validation that need to be addressed, including but not limited to the following:

1. Duplicate fields in one statement, such as Effect, Action, or Resource must not be allowed
2. Incorrect shape/values must be disallowed. For example, null for Effect, [] for Statement, [] for Resource, duplicate s3:prefix, non-homogeneous array value of s3:prefix, etc.
3. Unsupported fields in a statement must be disallowed, such as NotAction.
4. Missing required fields in Statement, such as missing Action, or Resource, etc must be disallowed.

This ticket tightens the validation.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-16274

How was this patch tested?

unit tests